1. Field of the Invention
The present invention relates to a tool and a method for using the tool for resetting a safety valve installed on a propane tank.
2. Description of Related Art
An overfill prevention device (“OPD”) is a safety valve incorporated into the filling valve of a liquefied petroleum gas, e.g. propane, tank. The OPD is designed to shut off the flow of gas to a tank after the tank has been filled to a predetermined capacity, e.g. 80% capacity. This allows the gas to expand when the tank is subjected to high temperatures, thereby minimizing the potential for an explosion. In the United States, as of Apr. 1, 2002, all propane tanks weighing between four and 40 pounds require the OPD as a safety device.
FIG. 1 illustrates the valve assembly 30 of a typical propane tank that is used in a variety of home applications. As shown in FIG. 1, the valve assembly 30 includes a main valve 34 that is manually operated with a rotatable handle 36 and an OPD 32 that is disposed within outlet 33. Without the OPD 32, there is no device to prevent gas from flowing out of the tank when the main valve is opened. Within the OPD 32 lies a spring biased safety valve 40 that is designed to cut off the flow of gas when there is nothing exerting pressure on it, such as a connected regulator, from the outside of the tank. This prevents the leakage of gas when the main valve 34 is not fully closed and there is nothing attached to the outlet 33 of the valve assembly 30.
Devices, such as barbeque grills, that utilize gas from propane tanks include regulators that attach directly to the propane tanks. FIG. 2 illustrates a regulator assembly 50 that includes an attachment portion 52 that is designed to engage the valve assembly 30 of FIG. 1 and provide a seal so that gas cannot escape around the regulator when the main valve is opened. The regulator assembly 50 also includes a safety device that ensures that the proper pressure is being used. Regulator assemblies 50 used in conjunction with propane tanks in the United States now require a thermal fuse as well as a spring loaded safety shut-off device 51. The safety shut-off 51 device typically includes a free floating ball bearing 60 and a spring 61 that biases the ball bearing 60 towards a closed position. The safety shut-off device 51 reacts to a dramatic increase in line pressure by fully biasing the ball bearing 60 to the closed position, thereby blocking flow of gas into the regulator 62. Also, if the regulator assembly 50 is exposed to excessive heat, the thermal fuse, which is made of a plastic material, will melt and thereby block the flow of gas.
Any impurities contained in the gas can create problems with the operation of the system, as any contaminants introduced by other means, such as such as dropping the regulator assembly 50 on the ground. Contaminants such as dirt or non-gaseous fuel can build up in the regulator assembly 50 and affect the proper functioning of the ball bearing 60 and spring 61. For example, contaminant build-up may cause the ball bearing 60 to stick in the closed position regardless of whether the safety shut-off device 51 has been tripped. For example, this may happen after the regulator assembly 50 is removed from the valve assembly 30 of the propane tank and the ball bearing 60 is allowed to move into the closed position via gravity, without the influence of the spring 61. Thus, if the ball bearing 60 is stuck in the closed position, the safety shut-off device 51 will not necessarily be fully reset upon attachment of the regulator assembly 50 to the tank valve assembly 30 because the flow of gas from the tank may not necessarily push the ball bearing 60 back to an open position.
The safety features of the OPD can create problems for those using propane tanks, particularly when the regulator assembly is removed from the tank and then reinstalled. Once the cut-off valve is engaged, which occurs when the regulator assembly is removed from the valve assembly, it should reopen by re-attaching the regulator assembly. However, the reattachment of the regulator assembly may not fully open the cut-off valve if the user neglects to fully re-attach the regulator assembly. This can impede the flow of gas by as much as 80%. Further, there may be a small volume of high pressure gas that gets trapped in a cavity between the main valve and the cut-off valve that further impairs the opening of the cut-off valve by creating extra resistance.
This problem has frustrated many users of gas tanks equipped with the OPD. Although there is typically some flow upon reattachment of the regulator assembly to the tank valve assembly, in many cases, the flow is not adequate to ensure the proper functioning of the device utilizing the gas.
For example, insect trapping devices, such as the device disclosed in U.S. Pat. No. 6,145,243, are specifically designed to utilize propane from a typical tank at a specific pressure. A regulator is used to deliver propane to the device at a constant predetermined pressure and the device performs a combustion operation to create a CO2 laden out flow for attracting insects. If the propane enters the regulator at a pressure below the predetermined level, the insect trapping device will not operate properly, as the out flowing CO2 content will be too low, or the combustion operation may not even commence. Thus, if the regulator assembly of an insect trapping device is not attached to the gas tank properly, the device may not function at all. This may be interpreted by the user as a problem with the insect trapping device itself rather than a problem with the propane tank connection.